![]() The applied reverse voltage establishes an electric field which acts in the same direction as the field due to potential barrier. To apply reverse bias, the positive terminal of the battery is connected to n-type and negative terminal to p-type of the pn junction as shown in fig.4. voltage applied to the junction is in such a direction that potential barrier is increased, it is called reverse biasing. Once the barrier is eliminated by the forward voltage, junction resistance becomes almost zero and a low resistance path is established for the entire circuit. Therefore, the resultant field is weakened and the barrier height is reduced at the junction as shown in fig.3.Īs potential barrier voltage is very small (0.1 to 0.3 V ), therefore, a small forward voltage is sufficient to completely eliminate the barrier. The applied forward potential establishes an electric field which acts against the field due to potential barrier. To apply forward bias, the positive terminal of the battery is connected to p-type and negative terminal is connected to n-type of the pn-junction as shown in fig.3. voltage applied to the junction is in such a direction that it cancels the potential barrier, thus permitting current flow, it is called forward biasing. ![]() In case of a pn junction, there are following two bias conditions: voltage to establish certain operating conditions for an electronic device. In electronics, the term bias refers to the use of d.c. The typical barrier potential is approximately:įor silicon, V 0= 0.7 V, For germanium, V 0= 0.3 V. There exist a potential difference across the depletion layer known as barrier potential (V 0). The positive and negative charges set up an electric field which acts as a barrier to the free electrons in the n region. In other words, the depletion layer acts as a barrier to the further movement of free electrons across the junction. Once pn junction is formed and depletion layer is created, the diffusion of free electrons stops. The depletion layer is formed very quickly and is very thin as compared to the n region and the p region. The term depletion is due to the fact that near the junction, the region is depleted i.e emptied of charge carriers (free electrons and holes) due to diffusion across the junction. These two layer of positive and negative charges form the depletion region or depletion layer. The result is that there is a layer of negative charges ( trivalent ions) near the junction. ![]() ![]() Properties of pn JunctionĪt the instant of pn-junction formation, the free electrons near the junction in the n region begin to diffuse across the the junction into the p region where they combine with holes near the junction.Īs a result n region loses free electrons and this creates a layer of positive charges (pentavalent ions) near the junction.Īs the electrons move across the junction, the p region loses holes as the electrons and holes combine. This button serves as a suitable base for soldering on leads. When all the germanium has been redeposited, the remaining material appears as indium button which is frozen on the outer surface of the crystallised portion as shown in fig.1(iii). The addition of indium overcomes the excess of electrons in the n-type germanium to such an extent that it creates a p-type region.Īs the process goes on, the remaining molten mixture becomes increasingly rich in indium.
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